Abstract
Cotton (Gossypium spp.) is the number one crop cultivated for fiber production and the cornerstone of the textile industry. Drought and salt stress are the major abiotic stresses, which can have a huge economic impact on cotton production; this has been aggravated with continued climate change, and compounded by pollution. Various survival strategies evolved by plants include the induction of various stress responsive genes, such as cyclin dependent kinases (CDKs). In this study, we performed a whole-genome identification and analysis of the CDK gene family in cotton. We identified 31, 12, and 15 CDK genes in G. hirsutum, G. arboreum, and G. raimondii respectively, and they were classified into 6 groups. CDK genes were distributed in 15, 10, and 9 linkage groups of AD, D, and A genomes, respectively. Evolutionary analysis revealed that segmental types of gene duplication were the primary force underlying CDK genes expansion. RNA sequence and RT-qPCR validation revealed that Gh_D12G2017 (CDKF4) was strongly induced by drought and salt stresses. The transient expression of Gh_D12G2017-GFP fusion protein in the protoplast showed that Gh_D12G2017 was localized in the nucleus. The transgenic Arabidopsis lines exhibited higher concentration levels of the antioxidant enzymes measured, including peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) concentrations under drought and salt stress conditions with very low levels of oxidants. Moreover, cell membrane stability (CMS), excised leaf water loss (ELWL), saturated leaf weight (SLW), and chlorophyll content measurements showed that the transgenic Arabidopsis lines were highly tolerant to either of the stress factors compared to their wild types. Moreover, the expression of the stress-related genes was also significantly up-regulated in Gh_D12G2017 (CDKF4) transgenic Arabidopsis plants under drought and salt conditions. We infer that CDKF-4s and CDKG-2s might be the primary regulators of salt and drought responses in cotton.
Highlights
Cell multiplication is controlled by conserved molecular machinery in which the main players are the Serine/Threonine kinases, known as cyclin-dependent kinases (CDKs)
All the CDKs in G. hirsutum, G. arboreum and G. raimondii had negative grand average of hydropathy (GRAVY) values ranging from −0.796 (Cotton_A_13019-CDKC-2) to −0.156 (Gh_A03G1965-CDKF-4), which implied that the cotton CDKs are hydrophobic, a property found to be common among the stress inductive genes, such as LEA genes
The CDKs were found to have low GRAVY values >0 and with high a charge ranging from −29.5 (Gorai.001G006600-CDKF-1) to 30.5 (Cotton_A_25379-CDKF-4), which is a unique feature observed among the CDK genes in Arabidopsis [27]
Summary
Cell multiplication is controlled by conserved molecular machinery in which the main players are the Serine/Threonine kinases, known as cyclin-dependent kinases (CDKs). CDKs are involved in mRNA processing, regulation of transcription, and in the differentiation of nerve cells in animals [3] They are found in all known eukaryotes, and their regulatory function in the cell cycle has been evolutionarily conserved, in plants, they are identified by both letters and numbers while in animals they are coded by numbers only [4]. As a consequence of plant lifestyle, plants are immobile for most of their lifetime and, lacking mobility, they have to cope with wide changes in their ecological niches Their successful adaptation to this sessile life-style can be attributed to their ability to adapt and respond to different types of biotic and abiotic stress. The cotton plant, known as white gold, is the number one fiber producing plant and the main source of raw materials for the textile industries [7]
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